RSC Mechanochemistry最新文献

Silicon carbide (SiC) is a critical material across structural, electronic, and catalytic applications; however, its conventional synthesis via the Acheson process is highly energy-intensive, operating at 2200–2400 °C with low carbon efficiency. Herein, we report a novel, solvent-free mechanochemical synthesis of mesoporous SiC using CO₂ as a sustainable carbon feedstock and SiO₂/Mg as earth-abundant precursors. Through a two-step ball-milling process, SiO₂ is first reduced by Mg to form Mg₂Si, which then spontaneously reacts with CO₂ to form SiC and MgO, achieving a high CO₂ conversion efficiency of 84% at only 10% of the energy cost of conventional methods. Density functional theory (DFT) calculations confirm the thermodynamic feasibility of CO₂ activation on Mg₂Si. The produced mesoporous SiC exhibited excellent durability and served as a highly stable support for Ni catalysts in dry reforming of methane (CH₄ + CO₂ → H₂ + CO), maintaining performance over 100 hours with minimal coke formation. This work introduces a green, scalable route for synthesizing high-value SiC, integrating CO₂ utilization and catalyst development under the principles of green chemistry.

Under solventfree mechanochemical conditions, treatment of Kobayashi's o-trimethylsilylphenyl triflate with tetrabutyl-ammonium fluoride hydrate (TBAF·H₂O) generates benzyne, which reacts with amines to give N-phenylated products.

NaTi₂(PO₄)₃, a NASICON-type sodium titanium phosphate (NTP), is a promising candidate for sodium-ion energy storage due to its robust structural and electrochemical properties. This study explores the impact of mechanochemical activation (MCA) on NTP synthesized via high-temperature methods, with a focus on sodium intercalation behaviour under various milling conditions. Sodiation experiments were performed in suspension using different sodium sources and the resulting structural and compositional changes after activation and the mean sodium content (〈x〉 defined as the average number of sodium ions per formula unit in Na_xTi₂(PO₄)₃) were determined by powder X-ray diffraction (PXRD) combined with Rietveld refinement as well as scanning electron microscopy (SEM), physisorption isotherm measurements, inductively coupled plasma mass spectrometry (ICP-MS), Raman spectroscopy and solid-state NMR. While MCA did not induce a phase transformation, extended milling times led to reduced crystallite sizes and increased structural disorder. The extent of sodium incorporation was strongly influenced by both the milling duration and the chemical nature of the sodium source, particularly its ability to reduce titanium. The highest sodium content of 3.5 approaching the theoretical maximum of 4.0 (Na₄Ti₂(PO₄)₃) was achieved using sodium naphthalene as the sodiation reagent.

We present a solvent-free Sonogashira coupling of various para-substituted aryl halides with terminal alkyne using a palladium catalyst and copper (0) co-catalyst under mechanochemical conditions. This study investigates the critical components required for C–C bond formation and explores the in situ generation of an active catalyst from individual precursors traditionally used in solution-phase chemistry. We demonstrate the role of palladium [Pd (0)] in different metal forms (powder and foil) within a copper milling jar, highlighting the importance of thermal activation and ligand presence in generating a reactive catalytic species. Notably, Pd was found to embed into the copper surface, enabling multiple reaction cycles without additional Pd, as confirmed by surface analysis. Furthermore, thermal control of the reaction allows for chemoselective activation of one halide over another. Our findings provide insights into the development of catalytic systems during mechanochemical reactions from individual components, offering a cost-effective and sustainable approach to solvent-free organic transformations. This study underscores the potential of mechanochemical methods for designing reusable catalytic systems with enhanced efficiency and selectivity.

Metal oxides reduction is one of the most important steps in metal production, where hydrogen-based metallurgy would significantly reduce greenhouse gas emissions from this emission-intensive process. By using mechanical energy, mechanochemistry enables the reduction of metal oxides at lower temperatures or even room temperature, which could significantly reduce energy loss due to heat dissipation in metal production at high temperatures. However, increased water partial pressure from hydrogen-based reduction leads to limited reaction rates. Herein, we demonstrate a mechanochemical method for the reduction of nickel oxide, adopting a ball milling system under continuous hydrogen flow. Nickel oxide can be mechanochemically reduced at room temperature or with mild heating (100 °C) for faster water removal. 88 wt% of nickel could be reduced after 10 h of milling. Efficient mechanochemical reduction benefits from the generation of abundant oxygen vacancies, increased surface area, continuously renewed particle surface, and constant removal of moisture. Compared to traditional metal oxide reduction methods, hydrogen-based mechanochemical reduction offers a low-temperature metallurgical pathway with no direct carbon emissions.

Mechanochemical synthesis is a sustainable and scalable approach for producing halide perovskites, offering key advantages over traditional solution-based methods, such as solvent-free processing, improved stoichiometric control, and reduced toxicity. In this work, we present a detailed study on the mechanochemical synthesis of MAPbI₃ and MAPbBr₃ (MA = methylammonium), with real-time monitoring of temperature developed to optimize the grinding conditions. We find that the temperature increase primarily originates from mechanical impact rather than the exothermicity of the reaction and does not limit perovskite formation and quality. Ultra-pure MAPbI₃ is readily obtained in under 10 minutes, while MAPbBr₃ requires longer grinding times for complete conversion (30 min). Prolonged milling yields finer powders, which are essential for formulating well-dispersed, DMF-free inks. These inks enable the fabrication of one-step slot-die coated perovskite photodetectors under ambient conditions. Our findings highlight that real-time thermal diagnostics provides a valuable tool for optimizing mechanochemical synthesis protocols and the importance of powder refinement to achieve homogeneous films suitable for scalable optoelectronic applications.

Supported bimetallic nanoparticles (NPs) have evolved as promising candidates for heterogeneous catalysis. Among various synthesis methods, ball milling has recently emerged as an effective approach for the preparation of high performing catalysts in diverse applications. Recognizing that solid–gas interactions in such a solvent-free environment might be crucial, we investigated the influence of the gas atmosphere (oxidative, inert, and reductive) during ball milling on the structural and electronic properties of Pd–Cu alloy NPs supported on high surface area α-Al₂O₃. Milling under an oxidative atmosphere leads to Cu-segregation to the surface, forming CuO, PdO, and a small fraction of metallic Pd alongside the Pd–Cu alloy phase. In contrast, in the case of an inert atmosphere, the major phase is the Pd–Cu alloy with a very minimal fraction of unalloyed metallic components. Milling under a reductive atmosphere reveals reverse segregation with metallic Pd segregating to the surface. Additional thermal treatment further promotes the alloy formation in all cases, but oxide species from synthesis under oxidative atmosphere are retained. Unveiling structure–property correlations, the materials were tested in the catalytic selective hydrogenation of acetylene to ethylene in equimolar acetylene/ethylene mixtures under industrially relevant pressure. Results demonstrate that the ball-milling atmosphere significantly influences catalytic performance, driven by the structural and electronic variations induced during synthesis. This study underscores the critical role gas environments may have in mechanochemical processes and highlights their potential to fine-tune catalyst properties for improved performance.

We report a solvent-free mechanochemical approach for the C–H halogenation and nitration of arenes. In situ-generated oxygen-centered mechanoradicals readily oxidize halide or nitrite salts, enabling C–H functionalization of arenes. Radical trapping experiments confirm the involvement of bromine radical species, distinct from conventional solution-phase processes that predominantly proceed via brominium intermediates. This operationally simple and carbon-free strategy is further extended to solid-state vicinal dibromination reactions of unactivated alkenes.

Mechanochemistry has been shown to provide a greener alternative to chemical synthesis; however, challenges in establishing clear relationships between chemical reaction yields and operational reactor parameters, such as milling frequency, milling ball material properties, vessel material properties, and reactor geometries used in a mechanochemical synthesis, make optimizing reactor efficiency difficult. This study presents a force model that relates these reactor parameters to quantifiable impact forces within a vibratory ball mill. To validate this force model, we developed a method for integrated, real-time measurement of force ensembles in the reaction vessel by embedding piezoresistive sensors with fast response to capture impact dynamics at various milling frequencies and operational settings. We measured force using preground NaCl at different fill ratios and compared it to an adjusted Hertzian contact mechanics force model with fill factor. We found agreement between the measured and modeled impact force. At the macroscale, impact acts as an ensemble of forces dynamically applied to the reactants. By simulating the mechanical activation of an illustrative mechanochemical system with known energetics, we show that there is little to no difference in effect between using the mean impact force and force ensemble on the kinetics of a straightforward mechanochemical reaction. We also demonstrate kinetic energy quantification in the Knoevenagel condensation reaction of vanillin and barbituric acid to understand what fraction of kinetic energy goes toward mechanical activation. We observed that the energetics of high-frequency milling for this reaction system entail diminishing returns, reinforcing the notion that there can be an optimal balance between collision intensity, resulting impact forces, and productive energy usage. The developed toolset and models provide a framework for understanding mechanochemical activation in vibratory ball mills and optimizing reaction parameters for scale-up to other reactors.

This paper describes the development of a mechanochemical method for the synthesis of cyclic carbonate esters via CO₂ fixation on propargyl alcohols. This solvent-free process is rapid and occurs under ambient conditions, thus offering a sustainable and efficient alternative to conventional solvent-based protocols. The mechanochemistry, which utilises the energy generated from milling, has the advantage of minimising waste, reducing reaction times, and simplifying work-up. The developed protocol demonstrates broad functional group tolerance, high yields, and the elimination of complex setups, thus highlighting its potential for application in organic and pharmaceutical synthesis.